RFR(xxs): 8214229: Enable ShowRegistersOnAssert by default

[Thomas Stüfe]

Hi,

8191101 (Show register content in hs-err file on assert) added a small
facility which would show register content in hs-err files at the
point where asserts/guarantees happened.

This feature has been very useful to us, and since its inception has
been enabled by default in our nightlies without problems showing up.
So we would like to enable this feature by default .

Please note that this feature is stubbed out on Non-Linux platforms so
this only affects Linux.

Bug: https://bugs.openjdk.java.net/browse/JDK-8214229
cr: http://cr.openjdk.java.net/~stuefe/webrevs/8214229-enable-ShowRegistersOnAssert-by-default/webrev.00/webrev/

Thank you,

Thomas